Method and apparatus for supporting sheet material

ABSTRACT

An article which may be in the form of a flat sheet is supported at least partially by a plurality of jets of gas discharged upwardly against the article from discharge orifices while the orifices are moved in directions having horizontal components so that the sheet may be displaced in a horizontal plane. The orifices may be in the walls of cylinders which are then rotated so that the moving jets displace the sheet horizontally. Orifices may also be provided in the upper reach of a belt which passes over slots in a gas discharge chamber which is connected to a source of gas under pressure. Both a method and apparatus are disclosed.

United States Patent Inventors Emile Plumat Gilly;

Robert Van Laethem, Lover-val, both of, Belgium AppL No. 743,387 Filed July 9, 1968 Patented July 20, 1971 Assignee Glaverbel Watermael-Boitslort, Belgium Priority July 12, 1967 Luxembourg 54,091

METHOD AND APPARATUS FOR SUPPORTIN SHEET MATERIAL 16 Claims, 14 Drawing Figs.

US. Cl 271/59, 271/74 Int. Cl B6511 9/00 8651129124 Field 01 Search 302/29, 31; 271/74, 58, 59, 60, 48, 49, 50; 65/25 A, 182 A References Cited UNlTED STATES PATENTS 1,618,660 2/1927 Howard 65/35 X Primary Examiner.loseph Wegbreit Attorney-Edmund M. Jaskiewicz ABSTRACT: An article which may be in the form of a flat sheet is supported at least partially by a plurality of jets of gas discharged upwardly against the article from discharge orifices while the orifices are moved in directions having horizontal components so that the sheet may be displaced in a horizontal plane. The orifices may be in the walls of cylinders which are then rotated so that the moving jets displace the sheet horizontally. Orifices may also be provided in the upper reach of a belt which passes over slots in a gas discharge chamber which is connected to a source of gas under pressure. Both a method and apparatus are disclosed.

PATENTEDJULEOIHYI 3 593 990 sum 1 OF 5 FIG] II JVEITTUR EMILE PLUMAT ROBERT VAN LAETHEM m'rmerucy PATENTED 20197: 3 593 990 SHEET 3 U 5 l6 INVENTORS EMILE PLUMAT ROBERT VAN LAETHEM ATTORNEY PAIENTED JULZO [an 593 99 0 sum 4 UF 5 Fias.

INVENTOR 5 EMILE PLUMAT ROBERT VAN LAETHEM BY (H ATTORNEY SHEEI 5 [1F 5 F G 8 INVENTOR5 EMILE PLUMAT ROBERT VAN LAETHEM ATTORNEY METHOD AND APPARATUS FOR SUPPORTING SHEET MATERIAL The present invention relates to materials handling, more particularly, to a method and apparatus for conveying sheet material with a minimum of surface contact.

The handling of materials and articles whose surfaces are readily susceptible to damage from contact with other bodies presents a problem in materials handling. This problem is readily apparent during the manufacture of sheet materials or articles which in their finished state must satisfy high standards of specifications regarding surface finish. This is especially true when during the manufacturing process the articles undergo a state in which their surfaces are easily marred or damaged by any contact with other bodies or objects. This category of articles and materials particularly includes various flat glass products and manufactured articles having highly sensitive surface coatings, such as, for example, light-sensitive coatings.

In order to overcome this problem in materials handling it has been proposed to support rigid sheets of material on a bed or cushion of a pressurized fluid established by supplying gas under pressurebeneath the sheets through a number of upwardly directed discharge openings. However, it has been found that one disadvantage of supporting such an article on a static or substantially static cushion of gasis that the stability of the support depends to a large degree upon the surface area of the article exposed to the jets forming the gas cushion. When articles of different sizes are so handled during the same production line, it will be readily apparent that the degree of stability of the different sized articles will vary since the pressure exerted by. the gas cushion upon the articles willnot be uniform.

In an attempt to achieve greater uniformity of pressure exerted by the gas cushion, the gas forming the cushion was evacuated at several different points underneath the article being supported. However, evacuating the gas in this manner had the result of decreasing the pressure in the area of evacuation which, in turn, again contributed to the lack of uniformity in the pressure exerted by the gas cushion against the article. While it is virtually impossible to obtain a precisely uniform gas pressure under all portions of the supported article, it is believed that a greater uniformity of this pressure could be ob tained if some degree of movement might be imparted to the gas cushion rather than employing a substantially static cushion.

It is therefore the principal object of the present invention to provide a novel and improved method and apparatus for the handling of articles with a minimum of contact.

It is another object of the present invention to provide a method and apparatus of conveying articles supported upon a cushion of gas.

It is a further object of the present invention to provide a method and apparatus for achieving a greater uniformity of pressure in a gas cushion supporting an article during a manufacturing process.

The objects of the present invention are attained and the disadvantages of the prior art are overcome by the present invention which discloses an apparatus and method for conveying articles in the form of sheets when the article is supported by a cushion of gas. The method disclosed herein essentially comprises directing a plurality of jets of gas upwardly against an article to support the article. The jets are then moved in directions having horizontal components so that the article is displaced in a horizontal plane while supported by the cushion of gas formed by the jets. The jets may be moved in directions having arcuate paths so that they approach and depart from the article or the jets may be moved unidirectionally in a horizontal plane. The jets may either completely or partially support the article. When partially supporting the article freely rotatable rollers are also used to at least contact the article to provide some degree of support. By directing the horizontal components of the movement of the gas jets in the same direction, the gas jets will tend to displace the article in that direction. The present invention therefore provides for an article to be both supported and conveyed by the gas jets. The direction and rate of advance of the article can be varied by changing the direction of movement of some or all ofthe jets.

The apparatus according to the present invention essentially comprises gas discharge means which are movably mounted beneath the article to be conveyed with there being a plurality of orifices therein. The gas discharge means is connected to a gas supply means which in turn is connected to a source of gas under pressure. This gas is discharged upwardly against the article to be conveyed to define a plurality ofjets which in turn form a gas cushion to support the article. At least some of the orifices are directed upwardly at any one time to discharge jets of gas against the article. The gas discharge means is movable in such a manner that the orifices are moved in directions having horizontal components. As a result, the corresponding movement of the jets discharged from the orifices will displace the article in a horizontal plane. The gas discharge means may be in the form of a plurality of spaced parallel cylindrical members having the orifices in their cylindrical walls. The orifices may be helically arranged around the axis of each cylindrical member. The cylindrical members are rotated so that the jets of gas approach and recede from the article. The jets will then both support and convey the article.

Another form of gas discharge means comprises a stationary chamber having a plurality of parallel slots in the upper surface thereof. A belt having a plurality of orifices moves over the slotted surface and in close proximity thereto. Thus, as the gas is discharged through the slots and the orifices, the moving belt will cause the jets of gas to move horizontally. One reach of the apertured belt may form an actual wall of the stationary chamber.

Other objects and advantages of the: present invention will be apparent upon reference to the accompanying description when taken in conjunction with the following drawings wherein;

FIG. I is a top plan view of one embodiment of the articleconveying apparatus according to the present invention;

FIG. 2 is a sectional view taken along the line 11-11 in FIG.

FIG. 3 is a view similar to that of FIG. 1 but showing a modification of the article-conveying apparatus;

FIG. 4 is a sectional view taken along the line IV-IV in FIG.

FIG. 5 is a sectional view taken along the line V-V in FIG. 3;

FIG. 6 is a longitudinal sectional view of a portion of another modification of the present invention and is taken along the line VI-Vl in FIG. 7;

FIG. 7 is a transverse sectional view of a further modification of the apparatus and is taken along the line VII-VII in FIG. 6;

FIG. 8 is a partial sectional view similar to that of FIG. 6 and showing still another modification of the present invention;

FIG. 9 is a sectional view similar to that of FIGS. 6 and 8 and showing an additional modification of the present invention;

FIG. 10 is an elevational view of a portion of one of the rollers employed in the modification of FIG. 9;

FIG. 11 is a view similar to that of FIG. l0but showing another modification of the roller;

FIG. 12 is an end elevational view of a portion of the apparatus according to the present invention modified for handling curved sheet material;

FIG. 13 is a bottom plan view of the rollers of the apparatus shown in FIG. 12; and

FIG. 14 is a top plan view of the rollers of the apparatus shown in FIG. 12.

Proceeding next to the drawings wherein like reference symbols indicate the same parts throughout the various views a specific embodiment and modifications of the present invention will be described in detail. The invention will be described 'with respect to the handling of a sheet of glass but it is to be understood that the invention can also be used for handling articles of a variety of shapes of other materials including metal, plastics or ceramics. j

As may be seen in FIG. I one embodiment of the invention comprises a gas discharge or distributing chamber 1 fixedly disposed between two rotatable cylindrical drums 2 upon which is positioned an endless belt 3. The belt is movable so that the upper reach thereof moves in the direction of the arrow indicated at 4. Horizontal transporting rollers 5 and 6 are positioned upstream and downstream of the belt. The tops of the rollers 5 and 6 and the upper reach of belt 3 lie in substantially the same horizontal plane.

The upper surface of the chamber 1 is provided with a series of parallel longitudinally extending slots 7.-The distributing chamber 1 is connected to a gas supply reservoir through conduits 8a and 8b having control valves 90 and 9b therein respectively. The supply reservoir 10 is in turn connected to a source of gas under pressure, which is not illustrated, through a supply line having a control valve 11 therein.

The belt 3 is provided with a plurality of slots 12 arranged over the entire surface area of the belt as may be seen in FIG. 1. The slots are arranged in rows running longitudinally of the belt so that the slots in each row will pass above and cooperate with a corresponding slot 7 in the top wall of distributing chamber 1. The upper reach of the belt 3 is in close proximity and may even contact the slotted wall of the distributing chamber 1 as shown in FIG. 2.

In order to operate the apparatus illustrated in FIGS. 1 and 2, the valves 9a and 9b are first opened so'as to'admit a pressurized gas into the distributing chamber 1. The pressurized gas may be compressed air but it is apparent that any other suitable gas may be employed, depending upon the nature of the material to be conveyed. While not shown in the drawings, one of the drums 2 is drivingly connected through reduction gearing or the like to a source of power and driven to cause the belt to travel over chamber 1 in the direction of arrow 4. A sheet of glass indicated at 13 is placed on the transporting roller 5 which raises the sheet above the top reach of the belt.

The pressure of the gas in chamber 1 is maintained at such a level that the jets of gas discharged upwardly from the orifices 14 formed by the intersection of chamber slots 12 and belt slots 7 support the sheet 13 a short distance above the belt as shown in FIG. 2. The orifices 14 will move continuously in the direction of the arrow 4 so that the gas cushion formed by the jets of 'gas impinging on the underside of sheet 13 similarly moves in the direction of the arrow 4 todisplace the sheet 13 in this direction. By varying the speed of movement of the belt the speed at which the supported glass sheet is conveyed can either be increased or decreased or the sheet may be stopped at any location along the path of movement as defined by the belt.

It is apparent that by displacing the jet orifices in the direction of the arrow 4 the forces exerted upon the sheet 13 have horizontal components. These horizontal components of force contribute to the stability of supporting the article upon a cushion of gas. The stability of the supported article depends largely upon achieving uniformity of the supporting pressure exerted by the gas cushion. Even when the article is not being displaced the present invention still provides a very high degree of uniformity of supporting pressure. With the ap paratus according to the present invention, the supporting pressure will vary at every point beneath the article during the is apparent that gas escapes from under the surface of the article between those points upon which the jets of gas impinge.

This escape or evacuation of the gas will result in a decrease in supporting pressure at that point.

According to the present invention, however, it is possible to avoid the effects of this localized decrease in supporting pressure by rapidly displacing the jets relatively to the article as supported on the gas cushion.

According to the modification illustrated in FIGS. '3-5 the apparatus comprises an endless belt 15 mounted on cylindrical drums 17 within a distributing chamber 16. The drums 17 have curved generatrices similar in shape to the transverse curvature of the top wall of the chamber 16. The beltflS is also supported by a series of small auxiliary rollers 18, one series of which is illustrated in H0. 5, so that the top reach of the belt 15 moves in close proximity to the top wall of chamber 16. The chamber 16 contains a pressurized gas which is discharged upwardly in the form of a plurality ofjets through orifices l9 defined by the intersection of transverse slots 20 in the belt 15 with longitudinal slots 21 in the top wall of distributing chamber 16. There are also provided transporting rollers 23 and 24 having generatrices curved to conform to those of the drums 17. The transporting rollers are positioned upstream and downstream of chamber 16 with respect to the intended direction of movement of an article as indicated by the arrow 4. The transporting rollers carry curved glass sheets 22 onto and from the gas cushion upon which the sheets are supported and conveyed over the chamber 16.

In the modification illustrated in FIGS. 6 and 7 the gas discharge means comprises a series of hollow cylinders 26 rotatably mounted between horizontally extending members 27 supported on vertical uprights 28.'The peripheral walls of cylinders 26 are provided with perforations 29. The ends of the cylinders 26 are indicated at 30a and 30b with these ends communicating with gas supply chambers 31a and 31b respectively through end apertures 32a and 32b. The cylinder ends 300 and 30b are provided with external flanges 33a and 33b and fluidtight seals are formed between these external flanges and the gas supply chambers 31a and 31b.

The gas supply chambers 31a and 31b .are connected through pipes 34a and 34b having regulating valves 35a and 35b to a gas storage reservoir 36. The reservoir 36 is provided with a supply line having a control valve 37 therein and is filled with pressurized gas at a given temperature which may be ambient'temperature. The pipes 34a and 34b are connected through secondary pipes 38a and 38b having control valves 39a and 39b to a second gas storage reservoir 40 having a supply control valve 41. The second reservoir 40 is filled with gas under pressure but maintained at a temperature different from that of the gas in storage reservoir 36.

The spaces between cylinders 26 are partially occupied by freely rotatable rollers 25 which assist in supporting the sheet 43 and guide it as it is advanced by the jets of gas. The upward forces exerted by the gas jets can be adjusted to such a value that the contact pressure between the sheet 43 and rollers 25 is very little. The rollers 25 could be omitted and the sheet supported completely by the gas cushion. It is to be noted that continuous evacuation of gas from spaced points underneath the article is facilitated when a gas discharge structure in the form of perforated cylinders is employed.

in the operation of the apparatus is illustrated in FIGS. 6 and 7 hollow cylinders 26 which are drivingly connected to a source of power are rotated in the direction as indicated by the arrow 42-or in the clockwise direction as 'viewed in FIG. 6. This rotation of cylinders 26 will displace the sheet of glass 43 inthe direction indicated by the arrow 44. Valves 35a, 35b and 39a, 39b are opened to admit gases at predetermined pressures and temperatures into the cylinders 26. The gas is then discharged from the cylinders 26 through the orifices 29 in the form of jets. The sheet of glass is then introduced at the upstream end of the apparatus and advanced therethrough in the direction of arrow 44 by the horizontal components of the forces exerted on the sheet by the jets of gas which are discharged continuously from the orifices 29 in the rotating cylinders26. During the rotation of the cylinders, the orifices will move cyclically along arcuatc paths which approach and recede from sheet 43. After the gas from thcjets has impinged against the underside of sheet 43 it escapes away from undemeath the sheet from between successive cylinders.

The driving effect of the gas jets against sheet.,43 can be modified by inclining the orifices 29 with respect to the radii of the respective cylinders 26. As illustrated in FIG. 6, the axes of the orifices 29 extend radially within the cylinders. Vanes or baffles 109 may be positioned as illustrated in FIG. 6 to deflect the jets on one side of one or more of the cylinders. It is also possible to mask or block the orifices on one side by providing screens 110 also illustrated in FIG. 6.

During its advance or displacement, the sheet43 can be positively guided against any lateral displacement by providing an edge guide at one or both lateral faces .of the sheet. Such a guide may comprise a freely rotatable roller or a belt rotation about a vertical axis or. axes. In the apparatus illustrated in FIGS. 6 and 7, the sheet 43is retained against lateral displacement by the tops of the horizontal members 27 which project slightly above the plane of the bottom surface of the sheet 43.

The speed at which'sheet43 is advanced through, the apparatus can be varied by changing the speed of rotation of the cylinders and/or theoutput and pressure of the gas.

It is pointed out that in the above-described embodiment the article may be conveyed solely by thejets of gas. As a modification, the article may be supported completely by the gas jets impinging thereon and then conveyed by rollers, belts or the like engaging the sides of the article along the required path of movement. A very light contacting pressureagainst the sides or edges of the article is sufficient to convey the article when supported by gas.

In the modification of FIGS. 6 and 7 horizontal displacement of the article maybe avoided by individually controlling cylinders 26 so that different cylinders rotate alternatively in both directions. As a result, the horizontal components of the forces exerted by the jets against the sheet will balance each other and the article will remain stationary.

The pressure exerted against the article 43 by the rollers 25 can be reduced by the use of gas jets supporting partially the article so that the article is not damaged or marred in any way article tobe overcome, such as in accelerating, braking .or

decelerating, to wholly support the article by the action of the jets because the frictional contact of the gas with the article is considerably less injurious than any frictional contact result ing from slip between the article and a contacting roller. The likelihoodof such. slip .is greater as .the contact pressure between the article and the rollers decreases and is virtually inevitable if successive rollers rotating at different speeds are employed for-accelerating or decelerating the article. Further, control of movement of the article bythe gas. jets has the advantage in that the accuracy of the supporting rollers with respect to their surface finish or diameter is of markedly reduced consequence.

Proceeding next to FIG. 8, there is illustrated a portion of an apparatus according to the present inventionhaving lower and upper series of rotatingcylinders 45a and 45b respectively. These cylinders are similar to the cylinders 26 employed in the modification illustrated in FIGS. 6 and 7. A. sheet 46.is consheet in the direction 47 and at the same time exert a downward force against the sheet soas to prevent any lifting of the article if the velocity of gas discharge is increased in order to accelerate the advance of the article. While not shown in the drawing, the output and pressure of the gas from the rotating cylinders can be regulated independently for the two series of cylinders.

The action of the jest of gas discharged from the perforated cylinders can be further explained with reference to FIG. 9. A sheet 60, which may be of glass, rests upon rotatable cylinders 61, 62, 63 each of which is provided with peripheral orifices 64. The interior of the cylinder indicated at 65 is filled with gas under pressure and the cylinder is rapidly rotated in the direction indicated by the arrow 66. The jets of gas discharged through each orifice have a tangential velocity component so that the gas is discharged from the cylinder in a direction 67 which is not radial to the cylinder but tangential to an imaginary smaller coaxial cylinder indicated at 68. Actually, the jet of gas discharged from an orifice does not extend along a straight path 67 but curves rcarwardly from the: orifice in a direction opposed to the rotation of the cylinder. Thus, each jet striking the sheet 60 exerts thereon both a vertical force and, because of friction, a horizontal force. If the cumulative vertical forces exerted by the gas jets are greater than the weight of the sheet, the sheet lifts from the cylinders to be supported by a cushion of gas and is advanced under the action of the horizontal forces exerted by the jets of gas. If the vertical forces are insufficient to raise the sheet, the sheet remains in contact with the cylinders and advances by the combined action of the rotating cylinders and the gas jets. The sheet is only partially supported by the cylinders since some upward force sill be exerted by the rotating jets.

In FIGS. 10 and 11 there are illustrated particularly advantageous arrangements of orifices in a cylinder where the orifices are arranged in one or more helical series around the cylinder axis. With such an arrangement, the orifices located at successive positions along the length of the cylinder can sweep narrow paths which may be located very close together or even overlap without adjacent orifices being so close together that the mechanical strength of the roller is unduly weakened. In FIG. 10, the helices are of a small pitch with the axial distance between successive turns being about 10 mm. The perforations 71 are so arranged that the plane 73 of the circular path of a perforation of one helix lies between the planes 74 and 75 of the circular paths of two successive perforations of another helix.

Inthe arrangement of FIG. 11, there are provided six helices having a very wide pitch with the gap between die planes of the paths of two successive turns on one helix being divided by the planes of the paths of at least two orifices belonging to the other helices. Thus, the planes 76 and 77 of orifices in the two lower of the three helices which are partially indicated in FIG. ll are located between the planes 78 and 79 of the paths of two successive orifices in the top helix indicated at 72. The gaps 80 between the planes 76, 77, 78 and 79 can also be divided by the planes of the paths of orifices in the other helices whichdo not appear in FIG. 11 The helical arrangement of orifices on the cylinders also contributes to the uniformity of supporting pressure exerted by the gas cushion without positioning the orifices too close to each other on the surface of the cylinder..

When a plurality of parallel perforated cylinders are employed, it is preferable for the relative angular setting of the cylinders about their axes to be such that if the supported article is held stationary the surface areas of the article which are struck by jets from successive cylinders having the same plane of circular movement will not overlap.

The apparatus illustrated in FIGS. 12-14 is particularly adapted for handling curved sheet material. This apparatus essentially comprises a series of lower barrel-shaped perforated cylinders and a series of upper rollers having a conforming configuration. The drawings illustrate an assembly of rollers at only one position along the length of the apparatus and it is to ,responding with that of the generatrices of the cylinders 101.

The lateral edges of the sheets are indicated by the broken lines 103 in FIG. 13. The upper rollers 104 have concave profiles complementary to the convex profiles of the lower cylinders. The upper rollers 104 can be freely rotatable or driven so as to assist in the guidance of sheets 102. The upper rollers 104 may also be replaced by perforated cylinders so that the sheets 102 are supported between cushions of gas in a manner similar to that described for the structure shown in FIG. 8. A roller 69 rotatable on a vertical shaft 70 contacts the lateral edges of sheets 102 to positively guide the sheets through the apparatus.

Auxiliary rollers 105 can be mounted between the spaced end portions of the rollers to provide a more continuous support of the sheets. The rollers similarly may be perforated cylinders if so desired. In a similar manner, auxiliary top rollers 107 can be mounted between the spaced central portions of the upper rollers 104 with the rollers 107 being rotatable in suspended bearing mounts 108.

It is apparent that the apparatus as disclosed herein is intended primarily for handling materials in sheet form. However, a wide variety of shapes of articles may also be handled. Articles in the form of cylinders, tubes, blocks of cubic or other shape would require a different arrangement of the gasdischarging means in order to conform to the configuration of the article. In order to handle a cylindrically shaped article, perforated cylinders may be used having their axes of rotation on the arc of a circle surrounding the cylindrical article and parallel to the axis of the cylindrical article so that the cylinders partially surround the article. The perforated cylinders may all be rotated in the same direction wherein the jets of gas will rotate the supported article about its axis or the cylinders may be rotated in different directions. The cylindrical article may be also displaced axially, as described above which would be parallel with the perforated cylinders, while the cylindrical article is supported entirely or partially by the jets of gas.

Thus it may be seen that the present invention has disclosed a simple but effective apparatus and method for the supporting and conveying of articles, particularly in sheet form, with little or no physical contact. By directing jets of gas under pressure upwardly against an article the article is supported upon a cushion of gas. Then, by moving the jets in paths having horizontal components of direction the jets will exert both vertical and horizontal forces on the article and the article will be displaced in a horizontal direction. While the present invention is particularly adapted to the handling of glass other materials in sheet and other forms may be readily handled by the method and process disclosed herein.

It will be understood that this invention is subject to modification in order to adapt it to different uses and conditions and, accordingly, it is desired to comprehend such modification within this invention as may fall within the scope of the appended claims.

What we claim is:

1. In a method of conveying an article, the steps of discharging a plurality ofjets of gas from a gas supplied under pressure, successively directing the jets upwardly towards a surface of an article so that the jets impinge against the surface to support at least partially the article, moving the jets ofgas impinging on the article surface in directions having horizontal components, the jets moving along a continuous curved path as they approach and then immediately go away from the article surface.

2.ln a method as claimed in claim 1 with said jets being cylindrically arranged and rotated about the axis of the cylindrical arrangement.

3. In a method as claimed in claim I wherein only some of the directions have horizontal components so that the resultant force exerted by all of the jets is insufficient to displace the article horizontally.

4. In a method as claimed in claim 1 with the additional step of contacting the article with a rotating member when the article is supported by the jets to impart movement to the article in a particular direction.

5. In a method as claimed in claim 4 with the rotating member partially supporting the article.

6. In a method as claimed in claim 4 with the rotating member contacting a lateral surface of the article.

7. ln a method as claimed in claim 1 wherein after jets have swept in a direction a given area of the article surface other jets are displaced in substantially the same direction to sweep other areas of the article surface which are offset transversely with respect to the said direction but cover part of said given area.

8. ln a materials-handling apparatus for conveying an article, the combination of gas discharge means movably mounted beneath an article to be conveyed and having a plurality of orifices therein, means connected to said gas discharge means for supplying said gas discharge means with gas under pressure to be discharged through the orifices to define a plurality of jets, a portion of said orifices being directed upwardly at any one time so that the jets of gas discharged therefrom will at least partially support the article, said gas discharge means being movable to move said orifices in directions having horizontal components and each orifice proceeding along a continuous curved path as the gas discharge means approaches and goes awayfrom the article, said gas discharge means comprising at least one rotatably mounted cylindrical member with circumferentially arranged orifices in the peripheral wall thereof. 1

9. In a materials-handling apparatus as claimed in claim 8 with said cylindrical member being a roller contacting and supporting the article thereon.

10. In a materials-handling apparatus as claimed in claim 9 with there being a plurality of said cylindrical members disposed in spaced parallel relation.

11. In a materials-handling apparatus as claimed in claim 8 and further comprising means for positively guiding the article while supported on the jets of gas.

12. In a materials-handling apparatus as claimed in claim ll with said guiding means comprising at least one roller.

13. in a materials-handling apparatus as claimed in claim 12 with said roller contacting a side of said article to guide the same.

l4. ln a materials-handling apparatus as claimed in claim 12 and further comprising driving means operatively connected to said roller for driving the same.

15. in a materials-handling apparatus as claimed in claim 8 with said orifices being helically arranged around said rotatable cylindrical member. 7

16. In a materials-handling apparatus as claimed in claim 8 wherein each orifice acts along a portion of the article surface having a width greater than the distance between two adjacent paths of the orifices, two orifices proceeding along adjacent paths being so arranged that at a given time the orifices each act upon a zone of the article surface with the zones being spaced from each other in the direction of the orifice paths. 

1. In a method of conveying an article, the steps of discharging a plurality of jets of gas from a gas supplied under pressure, successively directing the jets upwardly towards a surface of an article so that the jets impinge against the surface to support at least partially the article, moving the jets of gas impinging on the article surface in directions having horizontal components, the jets moving along a continuous curved path as they approach and then immediately go away from the article surface.
 2. In a method as claimed in claim 1 with said jets being cylindrically arranged and rotated about the axis of the cylindrical arrangement.
 3. In a method as claimed in claim 1 wherein only some of the directions have horizontal components so that the resultant force exerted by all of the jets is insufficient to displace the article horizontally.
 4. In a method as claimed in claim 1 with the additional step of contacting the article with a rotating member when the article is supported by the jets to impart movement to the article in a particular direction.
 5. In a method as claimed in claim 4 with the rotating member partially supporting the article.
 6. In a method as claimed in claim 4 with the rotating member contacting a lateral surface of the article.
 7. In a method as claimed in claim 1 wherein after jets have swept in a direction a given area of the article surface other jets are displaced in substantially the same direction to sweep other areas of the article surface which are offset transversely with respect to the said direction but cover part of said given area.
 8. In a materials-handling apparatus for conveying an article, the combination of gas discharge means movably mounted beneath an article to be conveyed and having a plurality of orifices therein, means connected to said gas discharge means for supplying said gas discharge means with gas under pressure to be discharged through the orifices to define a plurality of jets, a portion of said orifices being directed upwardly at any one time so that the jets of gas discharged therefrom will at least partially support the article, said gas discharge means being movable to move said orifices in directions having horizontal components and each orifice proceeding along a continuous curved path as the gas discharge means approaches and goes away from the article, said gas discharge means comprising at least one rotatably mounted cylindrical member with circumferentially arranged orifices in the peripheral wall thereof.
 9. In a materials-handling apparatus as claimed in claim 8 with said cylindrical member being a roller contacting and supporting the article thereon.
 10. In a materials-handling apparatus as claimed in claim 9 with there being a plurality of said cylindrical members disposed in spaced parallel relation.
 11. In a materials-handling apparatus as claimed in claim 8 and further comprising means for positively guiding the article while supported on the jets of gas.
 12. In a materials-handling apparatus as claimed in claim 11 with said guiding means comprising at least one roller.
 13. In a materials-handling apparatus as claimed in claim 12 with said roller contacting a side of said article to guide the same.
 14. In a materials-handling apparatus as claimed in claim 12 and further comprising driving means operatively connected to said roller for driving the same.
 15. In a materials-handling apparatus as claimed in claim 8 with said orifices being helically arranged around said rotatable cylindrical member.
 16. In a materials-handling apparatus as claimed in claim 8 wherein each orifice acts along a portion of the article surface having a width greater than the distance between two adjacent paths of the orifices, two orifices proceeding along adjacent paths being so arranged that at a given time the orifices each act upon a zone of the article surface with the zones being spaced from each other in the direction of the orifice paths. 